Scroll compressor

A scroll compressor provided with a housing, a shaft having a crank part rotatably axially supported by said housing and partially offset, and a movable scroll having a spiral shaped blade and end plate and driven to orbit by the crank part of said shaft, and a fixed scroll having a spiral shaped blade meshing with the movable scroll and end plate and fixed to said housing, where when said movable scroll is driven to orbit by the crank part of said shaft, while a plurality of working chambers formed between the blade of said movable scroll and the blade of said fixed scroll move toward the center, the volumes of the working chambers are successively reduced and thereby the fluid is compressed in the working chambers,

• said scroll compressor further provided with:
• a middle housing provided as part of said housing behind said movable scroll for supporting a thrust load in an axial direction of said shaft acting on said movable scroll along with the rise in the compression pressure of the fluid in the working chambers;
• at least one ring-shaped groove forming a backpressure chamber in one of a back surface of the end plate of said movable scroll and a front surface of said middle housing facing and supporting the same;
• a passage for introducing high-pressure fluid into said ring-shaped groove;
• and
• at least one ring-shaped seal ring fit movably in said ring-shaped groove.